Use the server tags for dimensions and make watch_name optional.
Use the server tags for dimensions and make watch_name optional.

This allows us to stop creating templates with circular dependancies.

So we can change:
  cfn-push-stats --watch {Ref: TheAlarm}
to:
  cfn-push-stats

This makes it closer to AWS and actually better as users can add their
own dimensions via the tags.

Change-Id: I365ae57c2275a2d064075eb1b3e14aa1e418d1ee

openstack/heat-cfntools,bbandaru/heat-cfntools